To learn from my mistakes, I will share with you the RIGHT way to say “What did you do this weekend?” Thanks to Ryan, Celia Rose, 윤혜영, Erik Loinberger, Linn Roby, Peter Floyd, Andrew Yang, and Rob Julien who explained it to me. So nice to have people to help as I learn! ROKStars!

지난 주말에 뭐 했어요?

지난 is last. 이번 is this time.
지난 주말 is last weekend. 이번 주말 is this weekend.

In Korean, 이번 주말 is always always the future weekend.

지난 주말에 뭐 했어요? What did you do last weekend? (past)
이번 주말에 뭐 할 거예요? What are you going to do this weekend? (future)